Piezo electric crystal apparatus



Feb. 28, 1933. R. H. WORRALL 1,899,127

PIEZO ELECTRIC CRYSTAL APPARATUS Filed May 14, 1930 2 Sheets-Sheet l Ins-1. L

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PIEZO ELECTRIC CRYSTAL APPARATUS Filed May 14, 1930 2 Sheets-$heet 2 w, jm

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A TTORNEY Patented Feb..28, 1933 UNITE STATES PATENT OFFICE PIEZO ELECTRIC CRYSTAL APPARATUS Application filed May 14,

My invention relates broadly to constant frequency control apparatus and more particularly to a construction of mounting for a piezo electric crystal apparatus employed in frequency control systems.

One of the objects of my invention is to provide a constant frequency control apparatus having means for preventing fluctuations in temperature of a piezo electric crystal enclosed thereby under conditions of temperature changes exterior to the piezo electric crystal mounting.

Another object of my invention is to provide a construction of a piezo electric crystal holder wherein an intermediate heat absorption member may be supported within an enclosing container and associated with parts of the container for mounting a piezo electric crystal element within the container in such manner that fluctuation in temperature immediately surrounding the piezo electric crystal under conditions of temperature changes exterior to the container is pre- Vented.

A further object of my invention is to provide a method of pivotally mounting a piezo electric crystal element for oscillatory movement within a container for securing the maximum piezo electric eflect therefrom.

A still further object of my invention is to provide a construction of casing for a piezo electric crystal apparatus having large mass and conductive to heat whereby a con- 35 stant temperature may be maintained ith- 1n the container by virtue of the relatively large mass of the container independent of fluctuations of external temperature.

Other and further objects of my invention reside in the construction of piezo electric crystal apparatus as set forth more fully in the specification hereinafter following by reference to the accompanying drawings, in which:

Figure 1 is a top plan view of the piezo electric crystal apparatus of my invention; Fig. 2 is a longitudinal vertical section through the apparatus shown in Fig. 1 on line 2,2 thereof; Fig. 3 is a lateral crosssectional view through the piezo electric crystal container online 33 of Fig. 2; Fig. i

1930. Serial No. 452,486.

is a lateral cross-sectional View taken through the piezo electric crystal container on line 4- of Fig. 2'; Fig. 5 is a plan view showing the interior arrangement of the piezo electric crystal apparatus on line 5-5 of Fig. 2; and Fig. 6 is a perspective View of the base member employed in the piezo electric crystal apparatus of my invention.

In the control of frequency in signaling systems, itis necessary that conditions in the immediate vicinity of the frequency control element be maintained constant. This is particularly true in a frequency control device of the piezo electric type. In a piezo electric crystal control apparatus, it is of the utmost importance that conditions of temperature and mechanical vibrations be maintained constant. The piezo electric crystal apparatus of my invention was developed to prevent fluctuations of temperature exterior to the crystal container from effecting variations in temperature immediately adjacent the piezo electric crystal element within the container. I provide a container having heavy metal walls having a high degree of heat conductivity and being massive in its structure. The large mass of metal serves as a heat reservoir and opposes any sudden changes of temperature. I mount the piezo electric crystal element within the heat conductive container in a novel manner which further protects the crystal against variations in temperature which might occur in the metal container. That is, a massive supporting plate of heat conductive material is supported within the container upon strips of insulation, the temperature of the IH1SSl"6 supporting plate being substantially unaffected by temperature changes exterior to the heat conductive casing. Measurements 90 taken over a long period of time to determine temperature changes immediately adjacent the piezo electric crystal have shown that the ratio of change in temperature between 5 the air surrounding the container and the container itself averaged M to 1. That is, if the air changed in temperature 1.1 the holder would change in temperature less i.01. The heat conductive properties of 100 the casing and the supporting plate which is mounted Within the casing are such that the 'arsfrom disturbin the mountin of the crystalwithin the container. 7

Referring to the drawings in more detail,

the container for the piezo electric crystal is.

indicated by reference character 1 havino heavy metallic walls app oximately one-half inch thick and having top closure 2 and a 7 lower closure 3 arranged as illustrated. The top closure 2 1s apertured ad acent the center thereof as indicated at 4:, and the apertur d portion 4 havingannular recesses 5 and 6 therein for receiving the insulated discs and 8 which serve to center the binding post9 which extends through the discs C and 8 with separator bushing 10 disposed between the CllSCS. Binding post 9 is supported upon the insulated laterally extending frame member 11 which is supported atone edge thereof by means of upwardly extending screw members 12 and 14: which project from the massive metallic base member 15. The base member 1 15 is rovided with laterall extending ribs illustrated at 16 and 18 which directly support the plate member 15 upon insulated strips 20 and 21 which are carried by opposite edges of the lower closure 3. Thelower 1 closure 3 is shown more clearly in Fig. 6 as comprisinga plate having a central recess 22' therein with'oppositely positioned recesses 23 and 24 in the sides of the recess 22in the lower closure 3. The lower closure 3. has vertically extending projections 25 and which support the insulated strips 20 and 21. The insulated strips 20 and 21 are each anchored into the plate 15 by screw members indicated at 20a and 21a thereby enabling the massive plate 15 to be supported within the container spaced from the inte ior walls thereof to allow the passage of convec-' tion currents "freely around the edges of the plate member.- The fact that casing 1 is massive and of dimensions of the order stated, gives it large heat storage capacity and effectively prevents short period. iations of the outside temperature from reaching the 7 interior of the casing; The piezo electric crystal isshown at2'? resting with its lower face directly in Contact with the upper surface of the massive plate 1.5; The crystal 2? is drilled at opposite I 27a'an'd 27b to receive the endsfof pins 28a and 28 which. are carried by-supportin members 2964 and 29bxwhiclr edges as indicated at are mounted upon the massive plate 15. The surface of plate 15 is crowned as shown in Fig. 2 to assist in the freevibration of the piezo electric crystal element. The plate 15 is connected through screw device 14 and connector 30 and screw 31to the interior wall of the casing 1 thus establishing connection between the lower faceofthe piezo electr c orv ment and an eX"" na-l circuit connection which may be made to outer casing l. The upper surface'of the piezo electric crystal element 27 is connected to binding post 9 by means of conductive strip 32 which connects through flexible lead 33 to the binding post 9. This conductive strip 32 which constitutes the upper electrode of the crystal may be conveniently formed by sputtering platinumon the crystal surface. The large mass of the container enables an even temperature to be maintained within the container andthe interposition of plate member 15 further in- V creases the degree of accuracy to which the tempcratm'e withinthe casing maybe maintained. The metallic plate 15 is preferably made. of invar metal having a very low coefficient of expansion, thus increasing the accuracy of the frequency control system. 7

The container may be mountedin a shock proof suspension and by reason of its large inei the crystal is protected against heavy shocks. 1 assemble the container of the piezo electric crystal apparatus by means of screw 7 members 3 land35 so that they may be readily removed for disassembly of the container. Removal of certain sets of the screws enables the sides of the container to be independently removed without disturbing the arrangement of the crystal within the container to permit of inspection and repair. Electrical connections are made to the piezo electric crystal apparatus between binding post 9 and the casing 1 by means of the screw indicated at 36.

ln r order to determine the temperature of the piezo electric crystal apparatus, a thermom:

eter well may be directly connected'to one side of the casing 1 and the thermometer inserted therein to determine thetempcrature conditions of the paratus.

The apparatus of my invention has been found to be highly practical in its construction and efiicientin itsoperation, and while I have described the apparatus in a certain preferred embodiment, I desire thatit be understood that modifications may be made and that nolimications upon my invention piezo electric crystal apare intended other than are imposed bythe V i scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows V 1. Piezo electric crystal apparatus comprising metallic casing of large heat storage capaclty, insulation 7 members extending transversely across the bottom of said casing, a plate member carried by said insulation members, a piezo electric crystal supported upon said plate member whereby said plate member provides electrical connection with the lower surface of said piezo electric crystal, and means extending through said casing but insulated therefrom for establishing electrical connection with the upper surface of said piezo electric crystal.

2. Piezo electric crystal apparatus comprising a heat conductive casing, heat insulation members extending transversely across the bottom of said casing, a metallic plate member supported by said heat insulation members, a piezo electric crystal supported by said plate member whereby said plate member provides an electrical connection with the lower surface of said piezo electric crystal, a bridge member supported in conductive contact by said plate member, a terminal post extending through said conductive casing and supported by said bridge member but insulated from said casing, and means connected with said terminal post for establishing connection nitli the upper surface of said piezo electric crystal.

3. Piezo electric crystal apparatus comprising a heat conductive casing, heat insulation members disposed interiorly of said casing and extending transversely across the bottom thereof, a heat conductive plate member supported by said heat insulation members, a piezo electric crystal element supported by said heat conductive plate member whereby said heat conductive plate member provides an electrical connection for the lower surface of said piezo electric crystal element, an insulated bridge member supported in conductive contact by said heat conductive plate member, a terminal post carried by said insulated bridge member and extending through said heat conductive casing, and a connection between said terminal post and the upper surface of said piezo electric crystal element.

4. Piezo electric crystal apparatus comprising a heat conductive casing of large heat storage capacity, heat insulation members disposed interiorly of said casing and c2:- tending transversely across the bottom thereof, a heat conductive plate member supported by said heat insulation members, a piezo electric crystal element supported by said heat conductive plate member whereby said heat conductive plate member provides an electrical connection for the lower surface of said piezo electric crystal element, a pair of standards projecting vertically from said heat conductive plate member, an insulation strip disposed between said standards, a binding post carried by said insulation strip and projecting through said heat conductive casing, and a connection between said binding post and the upper surface of said piezo electric crystal element.

5. Piezo electric crystal apparatus comprising a. heat conductive casing of large heat storage capacity, the lower portion of said heat conductive casing having a recess formed therein, a pair of heat insulation strips extending transversely across the recessed portion of said heat conductive casing, a heat conductive plate member supported by said pair of heat insulation strips, a piezo electric crystal element supported by said heat conductive plate member whereby said heat conductive plate member provides an electrical connection to the lower surface of said piezo electric crystal element, a standard projecting vertically from said heat conductive plate member, a laterally extending strip of insulation carried by said standard, a terminal post supported by said laterally extending strip of insulation and projecting through said casing but insulated therefrom, an electrode in fixed contact with the upper surface of said crystal element and a connection between said terminal post and said upper electrode.

6. In a piezo electric crystal apparatus, a massive metallic casing of large heat storage capacity, a massive plate member of heat conductive material supported within said casand spaced from the interior walls thereof for the circulation of convection currents therearound. a piezo electric crystal element supported by said plate member whereby said plate member provides an electrical connection for the lower surface of said piezo electric crystal, and conductive means insulated from said casing and projecting therethrongh for completing an electrical connection from the upper surface of said piezo electric crystal element.

7. Piezo electric crystal apparatus comprising a heat conductive casing, a pair of heatinsulation strips extending transversely across the bottom of said casing, a heat conductive plate member supported upon said strios, a piezo electric crystal element supported by said heat conductive plate member, whereby said plate member establishes electrical connection with the lower surface of said piezo electric crystal element, means supported by said plate member but insulated therefrom for establishing electrical connection with the upper surface of said piezo electric crystal element, and means carried by said plate member and projecting into diametrically opposite sides of said piezo electric crystal element for locating said piezo electric crystal element in position with respect to said plate member.

8. Piezo electric crystal apparatus comprising a heat conductive casing, a pair of heat insulation strips extending transversely acr ;s the bottom of said casing, .a heat con- (lllCtlVQ late member supported upon said strips, a piezo electric crystal element supported by said heat conductive plate mem- -be1- and extending into her, whereby said plate member establishes a electrical connection With the lower surface of said piezo electric crystal element, means supported by said plate member but insulated therefrom for establishing electrical connection With the upper surface of said piezo electric crystal element, said piezo electric crystal element having'bores formed in each edge of said piezo electric crystal element, and pin members carried by said plate memthe bores in the edges of said piezo electric crystal element.

ROBERT H; WORRALL] 

